Update Mission251Solution.ipynb

Mission251Solution.ipynb

@@ -32,7 +32,19 @@
    "cell_type": "code",
    "execution_count": 1,
    "metadata": {},
-   "outputs": [],
+   "outputs": [
+    {
+     "ename": "DuplicateDatabase",
+     "evalue": "database \"crime_db\" already exists\n",
+     "output_type": "error",
+     "traceback": [
+      "\u001b[0;31m---------------------------------------------------------------------------\u001b[0m",
+      "\u001b[0;31mDuplicateDatabase\u001b[0m                         Traceback (most recent call last)",
+      "\u001b[0;32m<ipython-input-1-cf6b3298b9db>\u001b[0m in \u001b[0;36m<module>\u001b[0;34m\u001b[0m\n\u001b[1;32m      5\u001b[0m \u001b[0mcur\u001b[0m \u001b[0;34m=\u001b[0m \u001b[0mconn\u001b[0m\u001b[0;34m.\u001b[0m\u001b[0mcursor\u001b[0m\u001b[0;34m(\u001b[0m\u001b[0;34m)\u001b[0m\u001b[0;34m\u001b[0m\u001b[0;34m\u001b[0m\u001b[0m\n\u001b[1;32m      6\u001b[0m \u001b[0;31m# create the crime_db database\u001b[0m\u001b[0;34m\u001b[0m\u001b[0;34m\u001b[0m\u001b[0;34m\u001b[0m\u001b[0m\n\u001b[0;32m----> 7\u001b[0;31m \u001b[0mcur\u001b[0m\u001b[0;34m.\u001b[0m\u001b[0mexecute\u001b[0m\u001b[0;34m(\u001b[0m\u001b[0;34m\"CREATE DATABASE crime_db;\"\u001b[0m\u001b[0;34m)\u001b[0m\u001b[0;34m\u001b[0m\u001b[0;34m\u001b[0m\u001b[0m\n\u001b[0m\u001b[1;32m      8\u001b[0m \u001b[0mconn\u001b[0m\u001b[0;34m.\u001b[0m\u001b[0mclose\u001b[0m\u001b[0;34m(\u001b[0m\u001b[0;34m)\u001b[0m\u001b[0;34m\u001b[0m\u001b[0;34m\u001b[0m\u001b[0m\n",
+      "\u001b[0;31mDuplicateDatabase\u001b[0m: database \"crime_db\" already exists\n"
+     ]
+    }
+   ],
    "source": [
     "import psycopg2\n",
     "conn = psycopg2.connect(dbname=\"dq\", user=\"dq\")\n",
@@ -46,18 +58,18 @@
   },
   {
    "cell_type": "code",
-   "execution_count": 14,
+   "execution_count": 2,
    "metadata": {},
    "outputs": [
     {
-     "ename": "NameError",
-     "evalue": "name 'psycopg2' is not defined",
+     "ename": "DuplicateSchema",
+     "evalue": "schema \"crimes\" already exists\n",
      "output_type": "error",
      "traceback": [
       "\u001b[0;31m---------------------------------------------------------------------------\u001b[0m",
-      "\u001b[0;31mNameError\u001b[0m                                 Traceback (most recent call last)",
-      "\u001b[0;32m<ipython-input-14-cf0881223d2f>\u001b[0m in \u001b[0;36m<module>\u001b[0;34m\u001b[0m\n\u001b[1;32m      1\u001b[0m \u001b[0;31m# now the crime_db database exists to we can connect to it\u001b[0m\u001b[0;34m\u001b[0m\u001b[0;34m\u001b[0m\u001b[0;34m\u001b[0m\u001b[0m\n\u001b[0;32m----> 2\u001b[0;31m \u001b[0mconn\u001b[0m \u001b[0;34m=\u001b[0m \u001b[0mpsycopg2\u001b[0m\u001b[0;34m.\u001b[0m\u001b[0mconnect\u001b[0m\u001b[0;34m(\u001b[0m\u001b[0mdbname\u001b[0m\u001b[0;34m=\u001b[0m\u001b[0;34m\"crime_db\"\u001b[0m\u001b[0;34m,\u001b[0m \u001b[0muser\u001b[0m\u001b[0;34m=\u001b[0m\u001b[0;34m\"dq\"\u001b[0m\u001b[0;34m)\u001b[0m\u001b[0;34m\u001b[0m\u001b[0;34m\u001b[0m\u001b[0m\n\u001b[0m\u001b[1;32m      3\u001b[0m \u001b[0mconn\u001b[0m\u001b[0;34m.\u001b[0m\u001b[0mautocommit\u001b[0m \u001b[0;34m=\u001b[0m \u001b[0;32mTrue\u001b[0m\u001b[0;34m\u001b[0m\u001b[0;34m\u001b[0m\u001b[0m\n\u001b[1;32m      4\u001b[0m \u001b[0mcur\u001b[0m \u001b[0;34m=\u001b[0m \u001b[0mconn\u001b[0m\u001b[0;34m.\u001b[0m\u001b[0mcursor\u001b[0m\u001b[0;34m(\u001b[0m\u001b[0;34m)\u001b[0m\u001b[0;34m\u001b[0m\u001b[0;34m\u001b[0m\u001b[0m\n\u001b[1;32m      5\u001b[0m \u001b[0;31m# create he crimes schema\u001b[0m\u001b[0;34m\u001b[0m\u001b[0;34m\u001b[0m\u001b[0;34m\u001b[0m\u001b[0m\n",
-      "\u001b[0;31mNameError\u001b[0m: name 'psycopg2' is not defined"
+      "\u001b[0;31mDuplicateSchema\u001b[0m                           Traceback (most recent call last)",
+      "\u001b[0;32m<ipython-input-2-cf0881223d2f>\u001b[0m in \u001b[0;36m<module>\u001b[0;34m\u001b[0m\n\u001b[1;32m      4\u001b[0m \u001b[0mcur\u001b[0m \u001b[0;34m=\u001b[0m \u001b[0mconn\u001b[0m\u001b[0;34m.\u001b[0m\u001b[0mcursor\u001b[0m\u001b[0;34m(\u001b[0m\u001b[0;34m)\u001b[0m\u001b[0;34m\u001b[0m\u001b[0;34m\u001b[0m\u001b[0m\n\u001b[1;32m      5\u001b[0m \u001b[0;31m# create he crimes schema\u001b[0m\u001b[0;34m\u001b[0m\u001b[0;34m\u001b[0m\u001b[0;34m\u001b[0m\u001b[0m\n\u001b[0;32m----> 6\u001b[0;31m \u001b[0mcur\u001b[0m\u001b[0;34m.\u001b[0m\u001b[0mexecute\u001b[0m\u001b[0;34m(\u001b[0m\u001b[0;34m\"CREATE SCHEMA crimes;\"\u001b[0m\u001b[0;34m)\u001b[0m\u001b[0;34m\u001b[0m\u001b[0;34m\u001b[0m\u001b[0m\n\u001b[0m",
+      "\u001b[0;31mDuplicateSchema\u001b[0m: schema \"crimes\" already exists\n"
      ]
     }
    ],
@@ -81,7 +93,7 @@
   },
   {
    "cell_type": "code",
-   "execution_count": 4,
+   "execution_count": 3,
    "metadata": {},
    "outputs": [],
    "source": [
@@ -105,7 +117,7 @@
   },
   {
    "cell_type": "code",
-   "execution_count": 12,
+   "execution_count": 4,
    "metadata": {},
    "outputs": [
     {
@@ -149,7 +161,7 @@
   },
   {
    "cell_type": "code",
-   "execution_count": 9,
+   "execution_count": 5,
    "metadata": {},
    "outputs": [
     {
@@ -166,7 +178,7 @@
   },
   {
    "cell_type": "code",
-   "execution_count": 8,
+   "execution_count": 6,
    "metadata": {},
    "outputs": [
     {
@@ -202,7 +214,7 @@
   },
   {
    "cell_type": "code",
-   "execution_count": 10,
+   "execution_count": 7,
    "metadata": {},
    "outputs": [
     {
@@ -258,18 +270,18 @@
   },
   {
    "cell_type": "code",
-   "execution_count": 5,
+   "execution_count": 8,
    "metadata": {},
    "outputs": [
     {
-     "ename": "ProgrammingError",
+     "ename": "DuplicateObject",
      "evalue": "type \"weekday\" already exists\n",
      "output_type": "error",
      "traceback": [
       "\u001b[0;31m---------------------------------------------------------------------------\u001b[0m",
-      "\u001b[0;31mProgrammingError\u001b[0m                          Traceback (most recent call last)",
-      "\u001b[0;32m<ipython-input-5-f43f3cb51339>\u001b[0m in \u001b[0;36m<module>\u001b[0;34m\u001b[0m\n\u001b[1;32m      4\u001b[0m cur.execute(\"\"\"\n\u001b[1;32m      5\u001b[0m     \u001b[0mCREATE\u001b[0m \u001b[0mTYPE\u001b[0m \u001b[0mweekday\u001b[0m \u001b[0mAS\u001b[0m \u001b[0mENUM\u001b[0m \u001b[0;34m(\u001b[0m\u001b[0;34m'Monday'\u001b[0m\u001b[0;34m,\u001b[0m \u001b[0;34m'Tuesday'\u001b[0m\u001b[0;34m,\u001b[0m \u001b[0;34m'Wednesday'\u001b[0m\u001b[0;34m,\u001b[0m \u001b[0;34m'Thursday'\u001b[0m\u001b[0;34m,\u001b[0m \u001b[0;34m'Friday'\u001b[0m\u001b[0;34m,\u001b[0m \u001b[0;34m'Saturday'\u001b[0m\u001b[0;34m,\u001b[0m \u001b[0;34m'Sunday'\u001b[0m\u001b[0;34m)\u001b[0m\u001b[0;34m\u001b[0m\u001b[0;34m\u001b[0m\u001b[0m\n\u001b[0;32m----> 6\u001b[0;31m \"\"\")\n\u001b[0m\u001b[1;32m      7\u001b[0m \u001b[0;31m# create the table\u001b[0m\u001b[0;34m\u001b[0m\u001b[0;34m\u001b[0m\u001b[0;34m\u001b[0m\u001b[0m\n\u001b[1;32m      8\u001b[0m cur.execute(\"\"\"\n",
-      "\u001b[0;31mProgrammingError\u001b[0m: type \"weekday\" already exists\n"
+      "\u001b[0;31mDuplicateObject\u001b[0m                           Traceback (most recent call last)",
+      "\u001b[0;32m<ipython-input-8-c6d02a51c525>\u001b[0m in \u001b[0;36m<module>\u001b[0;34m\u001b[0m\n\u001b[1;32m      1\u001b[0m \u001b[0;31m# create the enumerated datatype for representing the weekday\u001b[0m\u001b[0;34m\u001b[0m\u001b[0;34m\u001b[0m\u001b[0;34m\u001b[0m\u001b[0m\n\u001b[0;32m----> 2\u001b[0;31m cur.execute(\"\"\"\n\u001b[0m\u001b[1;32m      3\u001b[0m     \u001b[0mCREATE\u001b[0m \u001b[0mTYPE\u001b[0m \u001b[0mweekday\u001b[0m \u001b[0mAS\u001b[0m \u001b[0mENUM\u001b[0m \u001b[0;34m(\u001b[0m\u001b[0;34m'Monday'\u001b[0m\u001b[0;34m,\u001b[0m \u001b[0;34m'Tuesday'\u001b[0m\u001b[0;34m,\u001b[0m \u001b[0;34m'Wednesday'\u001b[0m\u001b[0;34m,\u001b[0m \u001b[0;34m'Thursday'\u001b[0m\u001b[0;34m,\u001b[0m \u001b[0;34m'Friday'\u001b[0m\u001b[0;34m,\u001b[0m \u001b[0;34m'Saturday'\u001b[0m\u001b[0;34m,\u001b[0m \u001b[0;34m'Sunday'\u001b[0m\u001b[0;34m)\u001b[0m\u001b[0;34m;\u001b[0m\u001b[0;34m\u001b[0m\u001b[0;34m\u001b[0m\u001b[0m\n\u001b[1;32m      4\u001b[0m \"\"\")\n\u001b[1;32m      5\u001b[0m \u001b[0;31m# create the table\u001b[0m\u001b[0;34m\u001b[0m\u001b[0;34m\u001b[0m\u001b[0;34m\u001b[0m\u001b[0m\n",
+      "\u001b[0;31mDuplicateObject\u001b[0m: type \"weekday\" already exists\n"
      ]
     }
    ],
@@ -303,18 +315,18 @@
   },
   {
    "cell_type": "code",
-   "execution_count": 13,
+   "execution_count": 9,
    "metadata": {},
    "outputs": [
     {
-     "ename": "NameError",
-     "evalue": "name 'psycopg2' is not defined",
+     "ename": "UniqueViolation",
+     "evalue": "duplicate key value violates unique constraint \"boston_crimes_pkey\"\nDETAIL:  Key (incident_number)=(1) already exists.\nCONTEXT:  COPY boston_crimes, line 2\n",
      "output_type": "error",
      "traceback": [
       "\u001b[0;31m---------------------------------------------------------------------------\u001b[0m",
-      "\u001b[0;31mNameError\u001b[0m                                 Traceback (most recent call last)",
-      "\u001b[0;32m<ipython-input-13-0d8c83600488>\u001b[0m in \u001b[0;36m<module>\u001b[0;34m\u001b[0m\n\u001b[0;32m----> 1\u001b[0;31m \u001b[0mconn\u001b[0m \u001b[0;34m=\u001b[0m \u001b[0mpsycopg2\u001b[0m\u001b[0;34m.\u001b[0m\u001b[0mconnect\u001b[0m\u001b[0;34m(\u001b[0m\u001b[0mdbname\u001b[0m\u001b[0;34m=\u001b[0m\u001b[0;34m\"crime_db\"\u001b[0m\u001b[0;34m,\u001b[0m \u001b[0muser\u001b[0m\u001b[0;34m=\u001b[0m\u001b[0;34m\"dq\"\u001b[0m\u001b[0;34m,\u001b[0m \u001b[0mpassword\u001b[0m\u001b[0;34m=\u001b[0m\u001b[0;34m\"dq\"\u001b[0m\u001b[0;34m)\u001b[0m\u001b[0;34m\u001b[0m\u001b[0;34m\u001b[0m\u001b[0m\n\u001b[0m\u001b[1;32m      2\u001b[0m \u001b[0mcur\u001b[0m \u001b[0;34m=\u001b[0m \u001b[0mconn\u001b[0m\u001b[0;34m.\u001b[0m\u001b[0mcursor\u001b[0m\u001b[0;34m(\u001b[0m\u001b[0;34m)\u001b[0m\u001b[0;34m\u001b[0m\u001b[0;34m\u001b[0m\u001b[0m\n\u001b[1;32m      3\u001b[0m \u001b[0;31m# load the data from boston.csv into the table boston_crimes that is in the crimes schema\u001b[0m\u001b[0;34m\u001b[0m\u001b[0;34m\u001b[0m\u001b[0;34m\u001b[0m\u001b[0m\n\u001b[1;32m      4\u001b[0m \u001b[0;32mwith\u001b[0m \u001b[0mopen\u001b[0m\u001b[0;34m(\u001b[0m\u001b[0;34m\"boston.csv\"\u001b[0m\u001b[0;34m)\u001b[0m \u001b[0;32mas\u001b[0m \u001b[0mf\u001b[0m\u001b[0;34m:\u001b[0m\u001b[0;34m\u001b[0m\u001b[0;34m\u001b[0m\u001b[0m\n\u001b[1;32m      5\u001b[0m     \u001b[0mcur\u001b[0m\u001b[0;34m.\u001b[0m\u001b[0mcopy_expert\u001b[0m\u001b[0;34m(\u001b[0m\u001b[0;34m\"COPY crimes.boston_crimes FROM STDIN WITH CSV HEADER\"\u001b[0m\u001b[0;34m,\u001b[0m \u001b[0mf\u001b[0m\u001b[0;34m)\u001b[0m\u001b[0;34m\u001b[0m\u001b[0;34m\u001b[0m\u001b[0m\n",
-      "\u001b[0;31mNameError\u001b[0m: name 'psycopg2' is not defined"
+      "\u001b[0;31mUniqueViolation\u001b[0m                           Traceback (most recent call last)",
+      "\u001b[0;32m<ipython-input-9-acb55cc3b2cf>\u001b[0m in \u001b[0;36m<module>\u001b[0;34m\u001b[0m\n\u001b[1;32m      1\u001b[0m \u001b[0;31m# load the data from boston.csv into the table boston_crimes that is in the crimes schema\u001b[0m\u001b[0;34m\u001b[0m\u001b[0;34m\u001b[0m\u001b[0;34m\u001b[0m\u001b[0m\n\u001b[1;32m      2\u001b[0m \u001b[0;32mwith\u001b[0m \u001b[0mopen\u001b[0m\u001b[0;34m(\u001b[0m\u001b[0;34m\"boston.csv\"\u001b[0m\u001b[0;34m)\u001b[0m \u001b[0;32mas\u001b[0m \u001b[0mf\u001b[0m\u001b[0;34m:\u001b[0m\u001b[0;34m\u001b[0m\u001b[0;34m\u001b[0m\u001b[0m\n\u001b[0;32m----> 3\u001b[0;31m     \u001b[0mcur\u001b[0m\u001b[0;34m.\u001b[0m\u001b[0mcopy_expert\u001b[0m\u001b[0;34m(\u001b[0m\u001b[0;34m\"COPY crimes.boston_crimes FROM STDIN WITH CSV HEADER;\"\u001b[0m\u001b[0;34m,\u001b[0m \u001b[0mf\u001b[0m\u001b[0;34m)\u001b[0m\u001b[0;34m\u001b[0m\u001b[0;34m\u001b[0m\u001b[0m\n\u001b[0m\u001b[1;32m      4\u001b[0m \u001b[0mcur\u001b[0m\u001b[0;34m.\u001b[0m\u001b[0mexecute\u001b[0m\u001b[0;34m(\u001b[0m\u001b[0;34m\"SELECT * FROM crimes.boston_crimes\"\u001b[0m\u001b[0;34m)\u001b[0m\u001b[0;34m\u001b[0m\u001b[0;34m\u001b[0m\u001b[0m\n\u001b[1;32m      5\u001b[0m \u001b[0;31m# print the number of rows to ensure that they were loaded\u001b[0m\u001b[0;34m\u001b[0m\u001b[0;34m\u001b[0m\u001b[0;34m\u001b[0m\u001b[0m\n",
+      "\u001b[0;31mUniqueViolation\u001b[0m: duplicate key value violates unique constraint \"boston_crimes_pkey\"\nDETAIL:  Key (incident_number)=(1) already exists.\nCONTEXT:  COPY boston_crimes, line 2\n"
      ]
     }
    ],
@@ -340,7 +352,7 @@
   },
   {
    "cell_type": "code",
-   "execution_count": 7,
+   "execution_count": 10,
    "metadata": {},
    "outputs": [],
    "source": [
@@ -361,9 +373,21 @@
   },
   {
    "cell_type": "code",
-   "execution_count": 8,
+   "execution_count": 11,
    "metadata": {},
-   "outputs": [],
+   "outputs": [
+    {
+     "ename": "DuplicateObject",
+     "evalue": "role \"readonly\" already exists\n",
+     "output_type": "error",
+     "traceback": [
+      "\u001b[0;31m---------------------------------------------------------------------------\u001b[0m",
+      "\u001b[0;31mDuplicateObject\u001b[0m                           Traceback (most recent call last)",
+      "\u001b[0;32m<ipython-input-11-aac7a30d6e63>\u001b[0m in \u001b[0;36m<module>\u001b[0;34m\u001b[0m\n\u001b[0;32m----> 1\u001b[0;31m \u001b[0mcur\u001b[0m\u001b[0;34m.\u001b[0m\u001b[0mexecute\u001b[0m\u001b[0;34m(\u001b[0m\u001b[0;34m\"CREATE GROUP readonly NOLOGIN;\"\u001b[0m\u001b[0;34m)\u001b[0m\u001b[0;34m\u001b[0m\u001b[0;34m\u001b[0m\u001b[0m\n\u001b[0m\u001b[1;32m      2\u001b[0m \u001b[0mcur\u001b[0m\u001b[0;34m.\u001b[0m\u001b[0mexecute\u001b[0m\u001b[0;34m(\u001b[0m\u001b[0;34m\"GRANT CONNECT ON DATABASE crime_db TO readonly;\"\u001b[0m\u001b[0;34m)\u001b[0m\u001b[0;34m\u001b[0m\u001b[0;34m\u001b[0m\u001b[0m\n\u001b[1;32m      3\u001b[0m \u001b[0mcur\u001b[0m\u001b[0;34m.\u001b[0m\u001b[0mexecute\u001b[0m\u001b[0;34m(\u001b[0m\u001b[0;34m\"GRANT USAGE ON SCHEMA crimes TO readonly;\"\u001b[0m\u001b[0;34m)\u001b[0m\u001b[0;34m\u001b[0m\u001b[0;34m\u001b[0m\u001b[0m\n\u001b[1;32m      4\u001b[0m \u001b[0mcur\u001b[0m\u001b[0;34m.\u001b[0m\u001b[0mexecute\u001b[0m\u001b[0;34m(\u001b[0m\u001b[0;34m\"GRANT SELECT ON ALL TABLES IN SCHEMA crimes TO readonly;\"\u001b[0m\u001b[0;34m)\u001b[0m\u001b[0;34m\u001b[0m\u001b[0;34m\u001b[0m\u001b[0m\n",
+      "\u001b[0;31mDuplicateObject\u001b[0m: role \"readonly\" already exists\n"
+     ]
+    }
+   ],
    "source": [
     "cur.execute(\"CREATE GROUP readonly NOLOGIN;\")\n",
     "cur.execute(\"GRANT CONNECT ON DATABASE crime_db TO readonly;\")\n",
@@ -384,9 +408,21 @@
   },
   {
    "cell_type": "code",
-   "execution_count": 9,
+   "execution_count": 12,
    "metadata": {},
-   "outputs": [],
+   "outputs": [
+    {
+     "ename": "DuplicateObject",
+     "evalue": "role \"readwrite\" already exists\n",
+     "output_type": "error",
+     "traceback": [
+      "\u001b[0;31m---------------------------------------------------------------------------\u001b[0m",
+      "\u001b[0;31mDuplicateObject\u001b[0m                           Traceback (most recent call last)",
+      "\u001b[0;32m<ipython-input-12-0e862a604f07>\u001b[0m in \u001b[0;36m<module>\u001b[0;34m\u001b[0m\n\u001b[0;32m----> 1\u001b[0;31m \u001b[0mcur\u001b[0m\u001b[0;34m.\u001b[0m\u001b[0mexecute\u001b[0m\u001b[0;34m(\u001b[0m\u001b[0;34m\"CREATE GROUP readwrite NOLOGIN;\"\u001b[0m\u001b[0;34m)\u001b[0m\u001b[0;34m\u001b[0m\u001b[0;34m\u001b[0m\u001b[0m\n\u001b[0m\u001b[1;32m      2\u001b[0m \u001b[0mcur\u001b[0m\u001b[0;34m.\u001b[0m\u001b[0mexecute\u001b[0m\u001b[0;34m(\u001b[0m\u001b[0;34m\"GRANT CONNECT ON DATABASE crime_db TO readwrite;\"\u001b[0m\u001b[0;34m)\u001b[0m\u001b[0;34m\u001b[0m\u001b[0;34m\u001b[0m\u001b[0m\n\u001b[1;32m      3\u001b[0m \u001b[0mcur\u001b[0m\u001b[0;34m.\u001b[0m\u001b[0mexecute\u001b[0m\u001b[0;34m(\u001b[0m\u001b[0;34m\"GRANT USAGE ON SCHEMA crimes TO readwrite;\"\u001b[0m\u001b[0;34m)\u001b[0m\u001b[0;34m\u001b[0m\u001b[0;34m\u001b[0m\u001b[0m\n\u001b[1;32m      4\u001b[0m \u001b[0mcur\u001b[0m\u001b[0;34m.\u001b[0m\u001b[0mexecute\u001b[0m\u001b[0;34m(\u001b[0m\u001b[0;34m\"GRANT SELECT, INSERT, UPDATE, DELETE ON ALL TABLES IN SCHEMA crimes TO readwrite;\"\u001b[0m\u001b[0;34m)\u001b[0m\u001b[0;34m\u001b[0m\u001b[0;34m\u001b[0m\u001b[0m\n",
+      "\u001b[0;31mDuplicateObject\u001b[0m: role \"readwrite\" already exists\n"
+     ]
+    }
+   ],
    "source": [
     "cur.execute(\"CREATE GROUP readwrite NOLOGIN;\")\n",
     "cur.execute(\"GRANT CONNECT ON DATABASE crime_db TO readwrite;\")\n",
@@ -407,9 +443,21 @@
   },
   {
    "cell_type": "code",
-   "execution_count": 10,
+   "execution_count": 13,
    "metadata": {},
-   "outputs": [],
+   "outputs": [
+    {
+     "ename": "DuplicateObject",
+     "evalue": "role \"data_analyst\" already exists\n",
+     "output_type": "error",
+     "traceback": [
+      "\u001b[0;31m---------------------------------------------------------------------------\u001b[0m",
+      "\u001b[0;31mDuplicateObject\u001b[0m                           Traceback (most recent call last)",
+      "\u001b[0;32m<ipython-input-13-87c28bfb320b>\u001b[0m in \u001b[0;36m<module>\u001b[0;34m\u001b[0m\n\u001b[0;32m----> 1\u001b[0;31m \u001b[0mcur\u001b[0m\u001b[0;34m.\u001b[0m\u001b[0mexecute\u001b[0m\u001b[0;34m(\u001b[0m\u001b[0;34m\"CREATE USER data_analyst WITH PASSWORD 'secret1';\"\u001b[0m\u001b[0;34m)\u001b[0m\u001b[0;34m\u001b[0m\u001b[0;34m\u001b[0m\u001b[0m\n\u001b[0m\u001b[1;32m      2\u001b[0m \u001b[0mcur\u001b[0m\u001b[0;34m.\u001b[0m\u001b[0mexecute\u001b[0m\u001b[0;34m(\u001b[0m\u001b[0;34m\"GRANT readonly TO data_analyst;\"\u001b[0m\u001b[0;34m)\u001b[0m\u001b[0;34m\u001b[0m\u001b[0;34m\u001b[0m\u001b[0m\n\u001b[1;32m      3\u001b[0m \u001b[0;34m\u001b[0m\u001b[0m\n\u001b[1;32m      4\u001b[0m \u001b[0mcur\u001b[0m\u001b[0;34m.\u001b[0m\u001b[0mexecute\u001b[0m\u001b[0;34m(\u001b[0m\u001b[0;34m\"CREATE USER data_scientist WITH PASSWORD 'secret2';\"\u001b[0m\u001b[0;34m)\u001b[0m\u001b[0;34m\u001b[0m\u001b[0;34m\u001b[0m\u001b[0m\n\u001b[1;32m      5\u001b[0m \u001b[0mcur\u001b[0m\u001b[0;34m.\u001b[0m\u001b[0mexecute\u001b[0m\u001b[0;34m(\u001b[0m\u001b[0;34m\"GRANT readwrite TO data_scientist;\"\u001b[0m\u001b[0;34m)\u001b[0m\u001b[0;34m\u001b[0m\u001b[0;34m\u001b[0m\u001b[0m\n",
+      "\u001b[0;31mDuplicateObject\u001b[0m: role \"data_analyst\" already exists\n"
+     ]
+    }
+   ],
    "source": [
     "cur.execute(\"CREATE USER data_analyst WITH PASSWORD 'secret1';\")\n",
     "cur.execute(\"GRANT readonly TO data_analyst;\")\n",
@@ -439,7 +487,7 @@
   },
   {
    "cell_type": "code",
-   "execution_count": 11,
+   "execution_count": 14,
    "metadata": {},
    "outputs": [
     {
@@ -501,7 +549,7 @@
    "name": "python",
    "nbconvert_exporter": "python",
    "pygments_lexer": "ipython3",
-   "version": "3.7.3"
+   "version": "3.8.2"
   }
  },
  "nbformat": 4,